Effect of MW-assisted roasting on nutritional and chemical properties of hazelnuts

Abstract

In order to enhance the flavor, texture, color, and appearance of hazelnuts, they are roasted during postharvest processing. In this study, raw hazelnuts (Corylus avellana L.) were roasted using microwave (MW) and MW-assisted hot air methods under various roasting conditions. The hazelnuts roasted were then examined to determine the percent DPPH radical scavenging activity, antioxidant capacity, total phenolic content, resistant starch, non-resistant starch, total starch, and protein concentration. The roasting experiments were done using a completely randomized factorial arrangement of two roasting types by three roasting times (9, 15, and 21 min) by three roasting temperatures (70, 90, and 110°C) using three replications within each experiment. These roasting methods were found to yield significant differences in antioxidant capacity, total phenolic content, resistant starch, non-resistant starch, and protein concentration between MW and MW-assisted hot air roasting processes, while no difference was found in percent DPPH radical scavenging activity and total starch. The results obtained may be of great importance to the food research community and industrial hazelnut roasting technologies.

Effects of Roasting Process on Color and Some Industrial Properties of Hazelnuts Cultivated By Organic And Conventional Methods

“…With the increase in the roasting temperature, there was a decrease in h* values in both cultivation methods (P˂0.05). Kalkan et al (2016) reported a similar result. Malekjani et al (2017) showed that the h value decreased with the increase in the roasting temperature and duration.…”

“…However, parallel to the increase in temperature, C* values of all samples were increased (P˂0.05). Chroma refers to color intensity (Kalkan et al, 2016). It was determined that hazelnuts had a more intense color with the increase in the roasting temperature.…”

Plant Specialized Metabolites in Hazelnut (Corylus avellana) Kernel and Byproducts: An Update on Chemistry, Biological Activity, and Analytical Aspects

“…Mostly, no statistical differences in total antioxidant activity have been observed among samples of unroasted and roasted kernels without skins; the thermal processing had a light negative trend in antioxidant efficacy mainly due to the absence of skins [1,27,50,52,59]. The effects of kernel roasting by 2 different processing methods, microwave and microwave-assisted hot air, revealed in both cases an increase of antioxidant activity at the rising of roasting time and temperature was observed, maybe explainable according to the formation of new Maillard reaction products having antioxidant activity [56,60].…”

“…An example of ellagitannin, in which at least 2 galloyl units are C-C coupled to each other, is represented by ellagic acid (56), found in the hazelnut kernel [23] (▶ Fig. 4).…”

“…The total antioxidant activities of the extracts obtained from hazelnut kernels, natural and roasted, with or without skins, differing for geographical origins, varieties, and storage conditions, have been measured [7,17,27,[49][50][51][52][53][54][55][56][57][58]. Mostly, no statistical differences in total antioxidant activity have been observed among samples of unroasted and roasted kernels without skins; the thermal processing had a light negative trend in antioxidant efficacy mainly due to the absence of skins [1,27,50,52,59].…”